High-reactance core-type transformer.



c. s. LAWSON HIGH REACTANCE CORE IYPE TRANSFORMER.

APPLICATION FILED APR. 4.1916.

Patented Aug. 13, 1918.

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0. s. LAWSON. HIGH REACTANCE CORE TYPE TRANSFORMER.

APPLICATION FILED APR- 4 I9I6.

Patented Aug. 13, 1918.

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INVENTOR iar/e5 J: [am/Jon WITNESSES:

ATTORNEY UNITED sures PATENT OFFICE.

CHAItnPi'ss. LAWSON, Q35 PITTSBURGH, PENNSYLVANIA. As'sI rNoR To WEST NGHOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

HIGH-REACTANCE' CORE-TYPE TRANSFORMER;

Specification Of Letters Patent.

Patented Au 13, 1918.

To all whom it may concern: y

Be it known that I, C ARLES S. LAWSON, a citizen ofthe United States, and a resident of Pittsburgh,.in the county of Allegheny and State ofPennsylvania, have invented a new and useful Improvement in High-Reactance Core-Type Transformers, of which theIfollowing is a specification.

My invention relates to electrical apparatus, and it has special relation to stationary alternating-current transformers of the core typeof construction.

More particularly, my inventionrela'tes to transformers of the above indicated character in which-it isv desired to secure high internal reactances in order to limit, to safe values, the currents that may flow through the windingsgof the transformers when they ,are subjected to short circuits or other conditions that mayoccasion the flow of abnormally high currents. Transformers embodyingmy invention may also be used in connection with rotary converters in" rder to provide an external reactance drop on the alternating-current side, thereby automatically compounding-the converters in a manner we'll-known in'the arty Core-type transformers, because of their form of construction, namely,;that of having a single magnetic circuit for'eachgroup .of coils, have-an inherently low internal reactance. In this respect, they difi er from shell-type transformers whiohthe several groups} of coils are surrounded or V inolosed by magnetizable material, thereby previeing a" plurality of magnetic circuits; for each group of coils. Since a core-type transformer has an inherently low internal reactance it is necessary to add a magneticleakage path or paths between its primary and secondary windings in order toincrease the internal reactance thereof to such a value as will protect the transformer frorn'the flow of abnormally high currents when it is subjected to short circuits or other conditions which tend to increase the current-flow to an abnormally high value. Of course, it will be understood that high-reactance transformers are frequently desired in connection with rotary converters in Order to automatically compound them, as mentioned above.

While the internal reactance of a coretype transformer may be substantially increased by adding magnetic leakage paths of relatively low reluctance for theleakage flux between the primary and secondary findings it isinecessary, especially in transformers adapted for high-voltage service,

to thoroughly insulate the several windings from one another and also from the core member. y v I V Fo the accomplishmentof the above mentioned objects,my present invention is particularly designed." meansof the present invention core-type transformers are pro} vided that have high internal reactances', and at the same time, are of a'simplfeform of construction which permits the primary and secondary windings to be adequately insulated from each other. Moreoventrans formers embodying" a form of my invention are easily assembled and only slightly more cumbersome than low internal reactance coretra'nsformersof the-usual type 77 7 F0 a t' 'ii un e tand slof t na u e a nclisc'ope of' my invention, reference may be had to the following descriptionandthe accompanying drawing in' which Figure 1' is side View of a core-type transformer that ei'nbOdiesa form of my i111vention;-Fig. 2 is an enlarged View, partially in elevation and partially inse'otion', ofia' portion of the transformer of F 1, showing, in" detail, the struct'ui-eb meansof which'I secure a high internal reactanc e, and Fig.3 is a plan view taken along the line 12 of Fig. 2; g

Referring to Fig. l, whioh shows a coretyp'e transformer, each' leg" 3 and 4: of a magnetizable core member 4* v is QIIIbTZI C Bd by coils 5 which constitute the low tfension winding of the" transformer and coils 6, spaced from the coils '5, which constitute the high-tension winding of' the transformer.

The coils 5an'd' 6"are insulated "from the core inernb'erby means of insulating washers'7'th'atj are'placedat the top and bottom oftheeore legs 3- and in order to space the windings from the yoke portions of-the core member. Between the'low-tensio'n coils 5 and the high-tension coils 6. I place himdles of magnetizable strips 8 by means of which 1 establish leakage paths 'of'low reluctan'c'e to enl'iance'the flow of the magnetic leakage flux between the primary andsecondary. windings. I propose to construct these leakage paths in theimanner shown in Figs, 2 and 3, to which reference may now be 'had.

tend beyond the core legs'3 andt a sufiicient distance, as shown, to substantially bridge the space between theilow tension or sec-u ondary coils 5 and the high-tension or primary coils 6. Each side of the cruciformcore leg 3 is provided with insulat ng covering 9 of channel shape which extends beyond the corners of the core leg in order to thoroughly insulate therefrom the immediately adjacent low-tension coil 5 WhlCll is wound in circular form in the usual manner. The low-tension winding, in this instance, comprises a plurality of coils 5 and 5 which are spaced from each other by means of wooden spacing strips 10 that are placed at intervals between these coils so as to provide a series of ventilating ducts 11 through which the insulating oil may freely flow. On two opposite sides of the core leg 3, I place a plurality of groups or bundlesS of magnetizable strips which are intermediate the low-tension coils 5 and 5 and the high-tension coils 6 and 6 The several groups 8 of'magnetizable strips are inter posed between the low-tensionand the hightension coils only at the places subtended by the yoke portions of the core member '1. The strips 8, therefore, form low-reluctance paths for the flow of the magnetic leakage flux, inasmuch asj'they are auxiliary, or placed in shunt, to the core leg 3 which is traversed by the main portions of the transformer flux, Each; bundle 8 of laminations is "bolted, at its top and bottom, to a segment12 of insulating material, preferably micarta, and to an insulating cylinder '13 which likewise maybe made of micarta.

' Bolts 14 extend through each bundle 8 of laminations and through the walls of the insulating barriers 12 and 13 in order to firmly hold the laminations in place and to permit the whole to be bodily lifted, when desired. As many bundles 8 are employed as are necessary to provide the required internal reactance and they are secured to the insulating cylinder 13 before assembling the transformer. The ends of the insulating segments 12 are bolted to wooden or insulating blocks 14 which, in turn, are secured to the insulating cylinder 13. In this manner, thespaces intermediate "the insulating segments 12 and the cylinder 13 that are occupied by the bundles 8 of laminations are closed, except for the vertical ventilating ducts intermediate adjacent bundles 8. Other wooden blocks 15 retain the insulating cylinder13 audits associatedstructure in a fixed position relative to the low-tension coils 5 and 5*. External to the insulting cylinder 13 are placed other wooden or insulatingblocks '16 which space the high-tension coils 6 from the insulating cylinder 13'. 'Anair gaps m'the magnetic circuit. By fjusting the number of' strips "18, the length other group of insulating. blocks 17 are in V terposed between the high-tension coils 6 and 6 in order to provide a plurality of vertical ventilating ducts therebetween.

From the foregoing description, it will be noted that auxiliary magnetic paths of relatively low reluctance are inserted below the low-tension coils 5 and 5 and the hightension coils 6 and 6 in order to increase the amount of leakage flux that may flow between the primary and secondary windings which, as is Well-known, increases the internal reactance of the transformer; The bundles 8 are so placed relative to the yoke portions and the core legs 3 and 1 of the transformer core that they provide paths for the magnetic flux whichare auxiliary to' the main paths furnished by the core legs 3 and 4:. In order' to regulate or adjust the quantity ofthe leakage flux traversing each auxiliary path, the bundles 8 may comprise a plurality of superposed groups 8* and 8 as shown in Fig; 2, which are spaced from one" another by means 'of insulating strips 18. The interpositioning of the insulating strips 1'8 is equivalent to providing ad of the air gaps may be regulated so as to vary, at will, the reluctance of the auxiliar paths provided by the bundles'S. V

From the foregoing description, it will be apparent that the high-tension and lowtension coils areadequately insulated from one another, and, atthe same time, have 'leakage'paths established therebetween by means of which a'nydesired amount of leakage may be directed from the main magnetic path. The bundles 8 are firmly secured in "place and, by reason of their being attached to the insulating'barriers 12 and 13, maybe readily applied when assembling the transformer. to While-I have shown and described one embodiment ofmy invention, it will be understood that many modifications may be made without departing from the spirit and scope of theappended claims. r I claim as my invention: 5 l. A transformer. comprising a core member, primary and secondary concentrically disposed and spaced coils embracing the same coreleg of said member, a cylindrical insulatlng barrier separating said coils from each other throughout their entire length and severally providing ventilating passa eways between, them, and magnetiza le shuntssecured to said barrier and placed to increase the leakage flux between said coils. 1

2. A transformer comprising a core member, concentrically disposed and spaced primary and secondary coils embracing a core leg thereof, an insulating barrier interposed between said coils, and a plurality of mag- 'netizable shunts secured to said barrier and disposed in parallel relationship to the core le s.

2%. A transformer comprising a rectangular core member having core legs and yoke portions, primary and secondary nested coils embracing the core legs, and a plurality of magnetizable shunts interposed between said nested coils which bridge the spaces subtended by the yoke portions only of the core.

4. A core type transformer comprising a rectangular core member having core legs and yoke portions, primary and secondary coils embracing the core legs thereof, insulating barriers interposed between the primary and secondary coils, and magnetizable shunts secured to the insulating barriers and bridging the spaces subtended by the yoke portions only.

5. A core-type transformer comprising a core member having core legs and yoke portions, primary and secondary coils embracing the core legs thereof, cylindrical insulating barriers interposed between the primary and secondary coils having magnetizable shunts attached to opposite sides thereof and bridging the spaces subtended by the yoke portions only.

6. A core-type transformer comprising a core member having core legs and yoke portions, the yoke portions extending laterally beyond the core legs, primary and secondary coils embracing the core legs, and magnetizable shunts extending between the laterally projecting yoke portions to increase the leakage flux between the primary and secondary coils.

In testimony whereof I have hereunto subscribed my name this 31st day of March,

CHARLES S. LAWVSON.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, I). 0. 

